Magnetic core and method of making same



June r10 1924.

y 1,497,469 B. AMES MAGNETIC CORE AND METHOD OF MAKING SAME Filed Feb. 1.0. 1919 Patented June l0,l1924.

uNiTED- STATES PATENT oFFicE.

BUTLER oELowELnimssacHUsnTTs.

.MAGNETIC conn AND METHOD or MAKING SAME.

i Application led February 10, 1919. Serial No. 276,006.

`a core which can be assembled both quickly and accurately, which iscompact and substantial. when assembled, which is peculiarly adapted to be im regnated with binding and insulating material, which has provision for being axially supported, which has provision for extending a conductor longitudinally therethrough, and which possesses any A two or more of the aforesaid characteristics in combination.

My improved core comprises a tubular casing, preferably cylindrical and of insulating material, partially or wholly filled with magnetic material, preferably pieces of iron wire extendin longitudinally of the tube. When the' tu ular casing is only partially filled with magnetic material, la smaller tubular member is preferablyv placed concentrically within the tubular `casin so that the magnetic material is. confine in the space between the two tubular parts. While the inner tube may be formed of insulating material it is preferably formed of metal in whichcase it is divided longitudinally to prevent eddy currents therein. A longitudinal opening may be provided in the core for a purpose which will hereinafter appear, in -which case a' channel member'of metal or other suitable material is preferably provided to separate the pieces of magnetic material from said space. r.

My improved methodrof making a core eof the character described comprises packtubes is being filled with magnetic materiah After the casing has Abeen filled with the magnetic material shellac or other insulating and binding material is foi'ced into the interstices between tlie pieces of magnetic material, the tubular construction lending itself peculiarly to this operation inasmuch as a stream of the sliellac or the like may be forced through the tubular Casin under pressure to carry away all air bub les and to ll every crevice between the Apieces of magnetic material.- After the core has been thoroughly impregnated the shellac or the like iscaused toharden, as by baking, to form a rigidand solid structure. If a longitudinal opening is to be provided in the core as above mentioned, a channel memberis preferably placed within the vtubular casing before the iron wires or the like are packed in to prevent the wires from filling the opening.

In the accompanying drawings- Fig. 1 is a central longitudinal section of one embodiment ofmy improved core;

Fig. 2 is an end elevation of the core shown in Fig. l;

Fig. 3 is a central longitudinal Section of a coil comprising a modified form of core; and Fig-4 is an end elevation of the coil and core shown in Fig. 3.

The particular embodiment of my invention illustrated in Figures 1 and 2 comprises a cylindrical casing A, preferably formed of fibre board or other hard insulating material, an inner tube B, preferably formed of iron and vpreferably divided longitudinally as shown at C to prevent the flow of eddy rrents, and a bundlelof iron wires D or ther suitable magnetic material packed ii to the space between the outer and inner tu es A and B. Before the parts are assein ed theyare preferably cut to the same length and the iron wires are inserted vinto the space between thetubes through one of the open ends. While the iron wires are being packed into the space between the tubes the two tubes are held concentric in any suitable manner. -After the parts have been assembled shellac or other suitable insulating and binding material is forced into the interstices between the wires. If the core is to be inserted into a magnetic circuit with its ends abutting against opposing faces of the circuit the ends of the core are preferably ground or machined to make them perfectly fiat and parallel and to afford good magnetic contacting surfaces.

The. heme or the like is preferably forced through the core by insertmg the core into a system of tubing so that a cur- Vrent of the' shellac or the vlike may be caused to iow through the core to driveout all the air and completely fill all of the open spaces between thel Wires. During this process the central opening may be plugged to l central tube -B is omitted, there would of course be no central opening through which passing through the axial opening. 2o

the shellac would tend to be shunted. However, it is ,preferable tomake the core hollouT for certain purposes in order to permit the core to be 'mounted by means of a rod the interstices'between the wires have been filled with shellac or the like the `-core is baked or otherwise treated to Vcause the shellac to harden. After the shellac has hardened the wires are bound tightly to'-4 gether and to the outer and inner tubes, thus forming a solid and rigid lcore.

The embodiment of my invention illustrated in Figs. 3 and4 is similar to that shown -in Figs ..1 and 2 except in that an opening F is provided longitudinally of the core to accommodate one of the leads (ir ot the electric coil H wound around the core. This longitudinal opening is preferably separatedfrom the iron Wires by means of a channel member K which is preferably V- shaped in cross-section as illustrated in Fig. 4. The channel member `K may be formed of fibre-board or'other hard insulating material or, -when the lead .G of the electric coil is grounded, they channel member may be formed of softiron or other metal. ,The

channel member'K is preferably placed in position before the iron wires are packed winding of the coil.

into the core so that it is held in position by the iron 4vwires and shellac applied thereto. v

When the core .is provided with Va longi, tu-dinal opening, as described, the inner lead of the surrounding. coil may be extended therethrough from one end of the-core to the opposite end, This'is of particular importance when the'winding appliedto `the core has an odd number of layers inasmuch as the inner lead of the coil can be bri-ight out at the same end of the coil as the outer leafd without in any way interfering with the If the coil is wound on the core the wire is .inserted through the 'opening L and thence extended throughthe opelnino F before the wire is Wound on the co1 plied to the core the lead G is inserted through the "opening, before the coilis slip ed over the core. The opening L is pre erably extended to the end of the tube Ff the coil' is wound before being ap? fectlyv round, when employing a round outer 4casi1 1g ,'andwhich forms a rigid and solid unit when completed. The construction makes it possible to grind. or machine the end faces without deforming the core, this being particularly important Where the core is to bel inserted into a magnet-ic circuit vas for example between the pole pieces of a magnetic'rotor as described in my prior application Serial No. 217,468, filed February 16, 191e. i

The peculiar construction of the electric,

around its inner peripheryy except for a longitudina'l space through which a conductor 'may extend, and an insulator separating said space from said magnetic material.

2. A magnetic core comprlsmg a tube of insulatingmaterial packed with pieces of' lating material into the tubular casing from one end to fill the interstices between the pieces of'magnetic material, at the same time forcing the air from the interstices through the other end of the tubular casing, and causing the insulating Vmaterial to harden. 5. method of making a magnetic core which niprises packing pieces of magnetic material in a tubular casing, connectles ing one end of the' tubular casing to a system of tubing and leaving the other end uncovered, and then flowing insulating material through the tubular casing .to drive out all the air and,toffill all the open spaces betweenthe pieces of'magnetic material.

'. Signed by me at Boston, Mass., this 23rd 4 dayof January, 1919.

. BUTLER AMES. 

